BH75 Hoses a popin !

[riprap]

I have a BH75 that I have not used much (say less than 10 hrs) that is about 6 years old - it has been stored indoors, and is in like-new condition. I use it on my B2630, which is used all the time and has given me no trouble at all - the loader has about 300hrs on it.

The problem is that I have had several strange hydraulic hose failures (1/8 inch or so blowouts).

The first failure was in the line from the swing valve to the distribution block - this is a stationary hose, is totally protected under the deck, doesn't move at all. I chalked it up to a manufacturing defect and replaced it. The line failed after 10-20 minutes of use.

The second failure happened in another hose for the swing circuit, this time one of the hoses that goes from the distribution block to one of the swing cylinders. The blowout occurred after only 15 minutes of mild use, the hydraulic fluid and lines were still at ambient temperature (70 deg ). Again a well protected, new looking, basically stationary and non-chafed line. Both blow-outs were 1-2 inches from the crimp.

Anyone have any ideas what could be going on ?

So far I have been lucky that these are easy access lines. Am I correct that this can't be a pressure relief problem - the loader has never had a problem - and these are 3000psi rated hoses - with the relief supposed to be set around 420psi ? (haven't measured it yet) - it would be a serious and obvious problem to get anywhere near that hose failure limit?

Anything special about the swing circuit ? Bad batch of hoses years ago ?

Any ideas but keep replacing them ?

Thanks all.

 

[leonz]

Hydraulic fluid under pressure
is like electricity and water-
its lazy and will escape
wherever and when ever
it can.


To begin with, the hoses are
10 years+ of age.


The rubber hose covering is
affected by the ozone in the
atmosphere.

The wire weaving for the hose
reinforcement is two wire braid.

You might simply have a weak spot
in the wire braid that finally gave way
where the hose might have been nicked
by a forklift fork that missed the pallet
picking the pallet up or the braiding wire
had a bad spot when the wire was formed
or when the hose was woven when the
hydraulic hose was made.


UNLESS you have a main relief valve on the
control valves for the back hoe your using the
main relief valve for the tractor only and it is
entirely possible that you had a spike in pressure
that found its way out.

 

[Egon]

Was the loader made by Kubota?

Sometimes you will find Kubota attachments that are painted the proper orange with Kubota decals but are actually outsourced.

 

[Stonehaller]

Might be worth taking apart and cleaning the valves for the swing circuit. Swing circuits generally have two pressure relief valves. In addition to limiting swing force these valves relief pressure from inertia of the hoe when you stop the swing. Perhaps one of your relief valves is stuck closed so the momentum of the hoe is over pressurizing the lines when you stop the swing.

 

[Kubota 2007]

Another thing to check is the Quick disconnects, the return may not be open completely or may have something restricting it. Check the easy things first. Having the return line blocked or restricted would act as the relief not working.
Another easy test is to "T" a gauge in the Pressure line (at the Quick Disconnect) start the tractor and read the gauge not using any functions, that will show "back pressure". Back Pressure shows the restrictions in the system, hose kinked, quick disconnect not full opening or blocked, you may have a hose that has come apart internally. Back Pressure should be no more than 100 psi. The less back pressure the better, ever pound of back pressure takes a pound of working pressure away. This is where I would start.

 

[riprap]

The loader is an LA403.

Thanks for the ideas guys.

One tiny detail that I hadn't considered is that this is the first time I have used an extension on one of the hoe quick connections - Anyone who has this set up knows how short the rear hydraulic hose is that goes to the hoe (and normally is looped back) - so this time I made up a 12" extension with quick connects so that I can power up the hoe a bit farther away than the normal 3" for installation. After the hoe was installed, I left the extension in place (could have unplugged it and plugged in direct).

I can't imagine what difference it made - but since this problem started with the extension it is very very suspicious -

 

[JoelD]

As others have mentioned I'd first check the relief valve (s), pull apart and ensure not seized up.

Joel

 

[riprap]

Does anyone know if the bh75 has a relief valve as part of the control assembly ? or does it only use the tractors limit ?

Also, what is the relief set to for the B series ? I saw a post talking about something like 420 psi, but that seems much too low.

 

[CHDinCT]

Check your manuals but your tractor's relief should be somewhere around 2300 - 2500 psi for your B. Also, most BH's have a relief valve as part of the BH valve/block or perhaps even a separate one for your swing circuit.

 

[riprap]

Check your manuals but your tractor's relief should be somewhere around 2300 - 2500 psi for your B. Also, most BH's have a relief valve as part of the BH valve/block or perhaps even a separate one for your swing circuit.

Thanks, Yes, I have verified that the swing circuit has its own relief cartridges and I will verify the setting as soon as I get a pressure gage.

I think I am on the right track with the quick connect jumper being the problem. On close inspection I notice that the OEM Snap-tite ISO B connectors have a thin/pointy actuating tip on the check valves - the one I used has a broader conical tip that may very well be causing some problem under some flow conditions (the connectors seat/connect fine).

This is a set I bought from ebay and they do not show a manufacturer on them (they seem very well made otherwise) - this is actually the second set I received from the same supplier - and in looking at the last set, the male connector has the thinned down actuating tip, but the female has the conical tip like the new set - this set had been working fine on a 3pt splitter for a year or so.

I am not sure how closely the ISO spec regulates the shape of this valve tip, but I will experiment with this a bit with a pressure gage to verify if this is the problem.

 

[riprap]

Well, After deciding that the connectors on the extension were the problem, I replaced the hose, removed the extension and went back to work....

And had ANOTHER hose blow out ! (after about 30 min of work)...

So, at this point I was sure it must have indeed been the relief valve (haven't received the JIC adapters need to measure pressure yet) - the hose was again in the swing circuit - so far 3 out of the 4 swing circuit hoses have failed....

So I backed the tractor into my garage and started to remove the hoe (I bypasses the swing circuit to stop the leak) - then all of a sudden I had a new leak from somewhere !... It turned out to be from the right side stabilizer - and on further inspection... the (retract) hose had blown also !

Now I was really stumped - the stabilizer doesn't even have a relief, much less the retract side - which never sees any pressure except when the stabilizer is at the top of travel....

I decided to cut into the hose where they blew out to see what the steel reinforcement looked like - (pictures below) - it looked corroded to me, so then I cut open a part that was OK, it looked like normal shiny steel. Then I inspected the hoses carefully and noticed that there were some lumpy areas - so I cut these open as well - and found a bunch of rust under the rubber outer layer !

So the problem is not relief pressure - it is that in at least 2 circuits, there is corrosion inside the hose reinforcing steel, causing them to lose strength.


I can't really imagine how this happened - the hoses are not damaged from the outside (the blow outs/rust areas) are not subject to any abrasion and the hoe has only been used a few hours. The hoe was bought new and used for a short time, then stored indoors for the last few years. The hydraulic fluid over that time was what came in the tractor new, after being removed the hydro hoses where plugged into each other...

Even if there was some moisture in the lines - I would have thought that there was rubber on the inside of the lines, embedding the steel, not leaving it exposed directly to the fluid...

SO- bottom line I inspected th hoses as best I could and found damage to all of the swing circuit lines (the last unfailed one) and both lines to the right side stabilizer. So far as I can tell (not very well) the lines to the working cylinders seem to be ok.

Next step is to get 4 more new lines and see what happens next.

Anyone ever seen anything like this ?

Also for anyone interested the differences in the QC tips - doesn't seem to be a problem...

 

[Egon]

It may be advisable to replace all the original hoses.

 

[CHDinCT]

Sounds like you're making headway on the issue but I'd still want to check the relief pressure when you have the new hoses installed. You might also consider changing out the hydraulic oil given the rust that may have entered the system. Hope your pressure issue is solved with the new hoses.

 

[riprap]

I dissected some more hose while waiting for more of the long 90 3/8 JIC to 1/4 hose ends to come in. I made some cuts across the rust bulges where the hose has not failed and it looks like both the inner and outer rubber is intact - so I am unsure of where or how the corrosion is happening.

The backhoe was last on the tractor when it was new, and the hydro oil was changed since then. It is really strange, there is no rust at all on the hoe, having been stored inside an unheated shed for the past 4 years, yet these hoses are rotting even though new in 2005.

I have had all kinds of equipment over the years, most quite old and abused with hoses old as heck and I never saw anything like this.

Just goes to show how true it is that leaving machinery idle is the hardest on it.

 

[RobKinNH]

I dissected some more hose while waiting for more of the long 90 3/8 JIC to 1/4 hose ends to come in. I made some cuts across the rust bulges where the hose has not failed and it looks like both the inner and outer rubber is intact - so I am unsure of where or how the corrosion is happening.

The backhoe was last on the tractor when it was new, and the hydro oil was changed since then. It is really strange, there is no rust at all on the hoe, having been stored inside an unheated shed for the past 4 years, yet these hoses are rotting even though new in 2005.

I have had all kinds of equipment over the years, most quite old and abused with hoses old as heck and I never saw anything like this.

Just goes to show how true it is that leaving machinery idle is the hardest on it.

Get the mfr name off the hoses and do a search. They might have had a bad batch of the steel reinforcement. They might even offer a replacement hose at a reduced cost.

 

[Egon]

Pin hole in outer covering, expansion , contraction, condensation.

 

[workinallthetime]

b3030 tlb 200+ hours. bh75, la403
i boke a BH hose at 15 hours within a month of purchase, since then i have replaced 4 hoses due to spontanious combustion i say. i think kubota didnt do a real good job on these or their supplier was the cheepest bid that year. I would have to admit im a little worried a hose will blow and shoot it the fluid into my eye, or cause me to drop a load "no pun intended".
i replace all mine with ones from a shop around here and those have yet to fail.

 

[riprap]

b3030 tlb 200+ hours. bh75, la403
i boke a BH hose at 15 hours within a month of purchase, since then i have replaced 4 hoses due to spontanious combustion i say. i think kubota didnt do a real good job on these or their supplier was the cheepest bid that year. I would have to admit im a little worried a hose will blow and shoot it the fluid into my eye, or cause me to drop a load "no pun intended".
i replace all mine with ones from a shop around here and those have yet to fail.

What year is your rig ? mine is a 2005

which hoses failed for you ?- same type of failure as I see - a blow out in the middle of the hose somewhere ?

For me the clincher was the stabilizer hose that raises the leg blowing - not exactly the most demanding part IMO.

 

[J_J]

This is my answer.

You can see where the hose has rubbed down to the metal.

http://www.tractorbynet.com/forums/hydraulics/221324-any-hydraulic-hose-experts-seen.html

You can set the relief lower on the BH, but never higher, because the PRV will control the system pressure.

Both reliefs can be set equal.

Has either relief been tested?

Someone may have cleaned the hoses with a chemical that made the rubber brittle.

 

[riprap]

This is my answer.

You can see where the hose has rubbed down to the metal.http://www.tractorbynet.com/forums/hydraulics/221324-any-hydraulic-hose-experts-seen.html...

Someone may have cleaned the hoses with a chemical that made the rubber brittle.

Thanks, however, you are mis-interpreting the photos -

The hoses are not rubbed down, what you see in the pictures is where I cut away the covering to see what the steel looked like - shiny in normal places and full of rust where the cover was bulged. The Hoses/Hoe were bought new in 2005, used only a tiny amount and then stored. The hoses are not brittle, look new, and have no wear on them at all. The hoe was never washed.

I will check the reliefs, but considering even the stabilizer raising hose failed, it is surely not a pressure problem. These hoses have a 12,000psi burst pressure - to have 5 blow out on very light use is impossible - hence it is clear that the problem is corrosion.

The question is how it happened and is there any countermeasures called for.